JP2013000761A - Rotary joining tool for friction stir joining and friction stir joining method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotary joining tool easy in control, comparatively inexpensive, affording favorable joining strength and used for joined members of different plate thicknesses, and to provide a friction stir joining method using the same.SOLUTION: Provided are the rotary joining tool for friction stir joining adapted to friction-stir-join the joined members of different plate thicknesses, wherein an upper base part, an upper shoulder, a lower base part, a lower shoulder and a probe between the shoulders are configured to be integrally rotatable, surfaces of the upper shoulder and the lower shoulder define a convex curve toward an abutment part, one or more grooves are formed in the convex curve so as to run from an outer periphery to the center and to flow the plasticized joined members into it, the abutment part of the joined members is nipped between the upper shoulder and the lower shoulder so as to set the probe parallel with abutment faces, and the probe moves along the abutment part while rotating with the upper base part and the lower base part out of contact with the joined members. A method of manufacturing the same is also provided.

Description

  In the present invention, a probe is provided between a pair of shoulders composed of an upper shoulder and a lower shoulder, a butted portion where the members to be joined are butted together is sandwiched between upper and lower shoulders, and the joint is friction stir welded by a rotating probe. More particularly, the present invention relates to a rotary joining tool for friction stir welding abutting portions of members to be joined having different plate thicknesses and a friction stir welding method using the same.

  As shown in FIG. 10, when the members 1 and 1 made of an aluminum material are subjected to friction stir welding, the members 1 and 1 are placed on the backing material 2 and abutted to each other. While rotating the probe, a probe (not shown) is inserted and a shoulder (not shown) is pressed against the members 1 and 1 to generate frictional heat, and the butted portion is stirred by the probe. At that time, in order to cope with this pressing load, the bonded member is supported by the backing material 2. This backing material 2 is installed in close contact with the back surfaces of the members 1 and 1 to be joined, and requires high rigidity. Conventionally, in friction stir welding, a friction stir welding method using a rotary tool called a bobbin tool instead of such a tool has been proposed.

  FIGS. 11A and 11B show friction stir welding using a bobbin tool described in Patent Document 1 below. In this friction stir welding method, the members 1 and 1 made of an aluminum alloy plate are butted against each other at the end faces, and friction stir welding is performed by the rotary welding tool 3. Specifically, the probe 31 shown in FIG. 11B moves along the abutting portion J. In FIG. 11, (b) is an AA cross-sectional view of (a).

  The probe 31 plastically fluidizes the surrounding members to be joined by mechanical stirring. The upper rotating body 41 and the lower rotating body 42 sandwich the member to be bonded from above and below, heat the member to be bonded by frictional heat, and prevent the material from being damaged from the plastic zone. Accordingly, when the rotary joining tool 3 moves along the abutting portion in this state, the softened material of the member to be joined flows behind the moving probe 31 while being plastically fluidized and agitated and kneaded. And the to-be-joined member which mutually crossed behind the probe is joined.

  However, in such a bobbin tool type rotary joining tool, the upper rotating body 41 and the lower rotating body 42 perform bonding by sandwiching materials. Therefore, when producing a differential thickness tailored blank material using a member to be joined that has a difference in thickness such that a level difference occurs at the abutting portion J, the rotating body does not contact the surface of the thin member to be joined, and the plasticized material is not. There was a problem in that normal joining could not be performed due to insufficient heat input that would flow out to the outside.

  Patent Document 2 describes a rotary bonding tool for obtaining a sound bonded portion even when a level difference occurs in a butted portion due to variations in the thickness of the members to be bonded. This rotary joining tool has a shoulder with a tapered shape, and a plurality of spiral grooves are formed on the surface thereof. The shoulder shape is tapered, and the shoulder tip is pushed into the material by a certain amount to absorb the level difference caused by the variation in the plate thickness. However, this rotary joining tool is for absorbing the thickness variation of the joined members having the same thickness, and is not intended for the joined members having different thicknesses. When this taper shape is applied to the differential thickness bonding, the taper angle must be increased, and the amount of the shoulder pushed into both the bonded members becomes large. As a result, there is a problem that the volume of the shoulder pushed into the thick plate bonded member becomes large and the heat input to the material becomes excessive, resulting in an increase in burr from the thick plate bonded member and a decrease in strength due to excessive heat input. It was. Furthermore, when the amount of pressing of the shoulder into the thin plate-joined member increases, there is a problem that the thickness of the joint portion decreases as the burrs from the thin plate-joined member increase.

  Patent Document 3 discloses a friction stir welding method in which no vibration is generated during the joining of the rotary joining tool even when a step occurs at the abutting portion or when the friction coefficients of the upper and lower surfaces of both joined members are different. The tool is listed. The upper and lower shoulder surfaces are provided with a plurality of concave grooves formed in the radial direction and the circumferential direction, and the surface of each block partitioned by the concave grooves is inclined in the rotational direction and / or the central direction. Thereby, even when there is a step at the butting portion, good bonding is possible. However, when the thick plate is applied to a difference thickness bonding between 2.0 mm and 1.0 mm to-be-joined members, the step is different. There was a problem that it was too large to achieve good bonding.

  Patent Document 4 describes a bobbin tool for differential thickness bonding or dissimilar metal bonding. By tilting the shoulder surface with the pressure adjusting device built in the shoulder, the rotating shoulder surface can always abut against both of the members to be joined even when a step occurs in the butted portion. As a result, even when the plate thickness is different and a step is generated at the abutting portion, the thickness difference bonding can be performed by the bobbin tool. However, since it is necessary to provide a pressure adjusting device applied to the shoulder surface inside the shoulder, there is a problem that the rotary joining tool becomes large and expensive. Furthermore, pressure adjustment is required depending on the plate thickness difference and material type, and there is a problem that the operation becomes very complicated and lacks practicality.

Japanese Patent No. 2712838 JP 2008-221338 A Japanese Patent No. 4292192 JP 2009-018312 A

  The present invention has been made in view of the above-mentioned problems of the prior art, and in friction stir welding of members to be joined having different plate thicknesses, rotary joining that is easy to control, is relatively inexpensive, and provides good joint strength. It is an object of the present invention to provide a tool and a friction stir welding method that is easy to operate and obtains good bonding strength.

The present invention provides a rotary joining tool according to claim 1, which is used for friction stir welding of butted portions of members to be joined made of metal plates having different plate thicknesses, the upper base portion having a substantially cylindrical shape; An upper shoulder provided on the bonded member side; a substantially cylindrical lower base; a lower shoulder provided on the bonded member side of the lower base; between the surface of the upper shoulder and the surface of the lower shoulder A probe connected to the upper base and the lower base concentrically with the upper base and the lower base;
The surfaces of the upper shoulder and the lower shoulder each form a convex curved surface toward the abutting portion, and in the convex curved surface, from the outer periphery to the center, and the joined member plasticized by the rotation of the rotary joining tool One or more grooves provided to flow into the interior are formed,
The abutting portion between the joined members is sandwiched between the upper shoulder and the lower shoulder so that the probe is parallel to the abutting surface of the abutting portion, and the upper base portion and the lower base portion do not contact the joined member A rotary welding tool for friction stir welding, in which the probe moves along the abutting portion while rotating in a state.

In the present invention, the curvature radii R ₁ (mm) and R ₂ (mm) of the convex curved surfaces of the upper shoulder and the lower shoulder satisfy the relationships of the following formulas (1) to (4), and The diameters D ₁ (mm) and D ₂ (mm) of the base and the lower base satisfy the relationships of the following formulas (5) and (6).
[4t ² −f ₁ ² − {(4t ² −f ₁ ² ) ² + 16f ₁ ² (t ² −T ² )} ^1/2 ] / 2 f ₁ ≦ g ₁ ≦ [4t ² −f ₁ ² + {( 4t ² −f ₁ ² ) ² + 16f ₁ ² (t ² −T ² )} ^1/2 ] / 2f ₁
time,
(F ₁ ² + 4t ² ) / 2f ₁ ≦ R ₁ ≦ {(g ₁ + f ₁ ) ² + 20T ² } / 2 (g ₁ + f ₁ )
(1)
If it is outside the above range,
{(G ₁ + f ₁ ) ² + 4T ² } / 2 (g ₁ + f ₁ ) ≦ R ₁ ≦ (f ₁ ² + 20t ² ) / 2f ₁
(2)
And
[4t ² −f ₂ ² − {(4t ² −f ₂ ² ) ² + 16f ₂ ² (t ² −T ² )} ^1/2 ] / 2f ₂ ≦ g ₂ ≦ [4t ² −f ₂ ² + {( 4t ² −f ₂ ² ) ² + 16f ₂ ² (t ² −T ² )} ^1/2 ] / 2f ₂
time,
(F ₂ ² + 4t ² ) / 2f ₂ ≦ R ₂ ≦ {(g ₂ + f ₂ ) ² + 20T ² } / 2 (g ₂ + f ₂ )
(3)
If it is outside the above range,
{(G ₂ + f ₂ ) ² + 4T ² } / 2 (g ₂ + f ₂ ) ≦ R ₂ ≦ (f ₂ ² + 20t ² ) / 2f ₂
(4)
And
D ₁ ≧ 2 {(2R ₁ −g ₁ −f ₁ ) (g ₁ + f ₁ )} ^1/2 (5)
D ₂ ≧ 2 {(2R ₂ −g ₂ −f ₂ ) (g ₂ + f ₂ )} ^1/2 (6)
Where, f ₁ : pressing amount of upper shoulder in thin plate joining member (mm), g ₁ : level difference (mm) of butt surface on upper shoulder side, f ₂ : pressing amount of lower shoulder in thin plate joining member (Mm), g ₂ : level difference (mm) of the abutting surface on the lower shoulder side, t: thickness (mm) of the thin plate joining member, T: thickness (mm) of the thick plate joining member.

  According to a third aspect of the present invention, in the third aspect, the upper base is provided with a large diameter or hexagonal main body on the side opposite to the upper shoulder.

  According to a fourth aspect of the present invention, the lower base is provided with a large-diameter or hexagonal main body on the side opposite to the lower shoulder.

The present invention is the friction stir welding method according to claim 5, wherein the members to be joined made of metal plates having different plate thicknesses are brought into contact with each other, and the members to be joined are joined by moving along the abutting portions while rotating the rotary joining tool. The rotary joining tool includes a substantially cylindrical upper base; an upper shoulder provided on the joined member side of the upper base; a substantially cylindrical lower base; and a joined member side of the lower base A lower shoulder provided; a probe connected between the surface of the upper shoulder and the surface of the lower shoulder and suspended concentrically with the upper base and the lower base; and is configured to be integrally rotatable.
The surfaces of the upper shoulder and the lower shoulder each form a convex curved surface toward the abutting portion, and in the convex curved surface, from the outer periphery to the center, and the joined member plasticized by the rotation of the rotary joining tool One or more grooves provided to flow into the interior are formed,
The abutting portion between the joined members is sandwiched between the upper shoulder and the lower shoulder so that the probe is parallel to the abutting surface of the abutting portion, and the upper base portion and the lower base portion do not contact the joined member The friction stir welding method is characterized in that the probe moves along the abutting portion while rotating in a state.

In the present invention, the curvature radii R ₁ (mm) and R ₂ (mm) of the convex surfaces of the upper shoulder and the lower shoulder satisfy the relationships of the following formulas (1) to (4), and The diameters D ₁ (mm) and D ₂ (mm) of the base and the lower base satisfy the relationships of the following formulas (5) and (6).
[4t ² −f ₁ ² − {(4t ² −f ₁ ² ) ² + 16f ₁ ² (t ² −T ² )} ^1/2 ] / 2 f ₁ ≦ g ₁ ≦ [4t ² −f ₁ ² + {( 4t ² −f ₁ ² ) ² + 16f ₁ ² (t ² −T ² )} ^1/2 ] / 2f ₁
time,
(F ₁ ² + 4t ² ) / 2f ₁ ≦ R ₁ ≦ {(g ₁ + f ₁ ) ² + 20T ² } / 2 (g ₁ + f ₁ )
(1)
If it is outside the above range,
{(G ₁ + f ₁ ) ² + 4T ² } / 2 (g ₁ + f ₁ ) ≦ R ₁ ≦ (f ₁ ² + 20t ² ) / 2f ₁
(2)
And
[4t ² −f ₂ ² − {(4t ² −f ₂ ² ) ² + 16f ₂ ² (t ² −T ² )} ^1/2 ] / 2f ₂ ≦ g ₂ ≦ [4t ² −f ₂ ² + {( 4t ² −f ₂ ² ) ² + 16f ₂ ² (t ² −T ² )} ^1/2 ] / 2f ₂
time,
(F ₂ ² + 4t ² ) / 2f ₂ ≦ R ₂ ≦ {(g ₂ + f ₂ ) ² + 20T ² } / 2 (g ₂ + f ₂ )
(3)
If it is outside the above range,
{(G ₂ + f ₂ ) ² + 4T ² } / 2 (g ₂ + f ₂ ) ≦ R ₂ ≦ (f ₂ ² + 20t ² ) / 2f ₂
(4)
And
D ₁ ≧ 2 {(2R ₁ −g ₁ −f ₁ ) (g ₁ + f ₁ )} ^1/2 (5)
D ₂ ≧ 2 {(2R ₂ −g ₂ −f ₂ ) (g ₂ + f ₂ )} ^1/2 (6)
Where, f ₁ : pressing amount of upper shoulder in thin plate joining member (mm), g ₁ : level difference (mm) of butt surface on upper shoulder side, f ₂ : pressing amount of lower shoulder in thin plate joining member (Mm), g ₂ : level difference (mm) of the abutting surface on the lower shoulder side, t: thickness (mm) of the thin plate joining member, T: thickness (mm) of the thick plate joining member.

  According to a seventh aspect of the present invention, in the seventh aspect, the upper base is provided with a large diameter or hexagonal main body on the side opposite to the upper shoulder.

  According to the present invention, in the eighth aspect, the lower base is provided with a large-diameter or hexagonal main body on the side opposite to the lower shoulder.

  The rotary joining tool according to the present invention is used for friction stir welding of members to be joined having different plate thicknesses, is easy to control, is relatively inexpensive, and provides good joint strength. Further, in the friction stir welding method using the present rotary welding tool, easy operation is possible and good bonding strength is obtained.

It is a front view which shows the rotary joining tool which concerns on this invention. It is a top view of the shoulder surface of the rotary joining tool which concerns on this invention. It is explanatory drawing showing the state which inserted the rotary joining tool in the butt | matching part. It is explanatory drawing for calculating | requiring the volume of the shoulder pushed in in a thick board. It is a perspective view showing the state which faced the thick board and the thin board. It is a perspective view showing the state before pushing into a butt | matching surface, rotating a rotary joining tool. It is a perspective view showing the state which inserts a rotary joining tool in a butt | matching part. It is a perspective view showing the state which is moving by moving the inserted rotary joining tool. It is a perspective view showing the state currently extracted from the abutting part, rotating a rotary joining tool. It is a perspective view explaining the conventional friction stir welding method. It is the perspective view (a) and front view (b) explaining the conventional friction stir welding method.

A. To-be-joined member Examples of the to-be-joined member made of a metal plate applicable to the friction stir welding according to the present invention include materials such as aluminum, aluminum alloy, copper, copper alloy, titanium, titanium alloy, magnesium, and magnesium alloy. Also, one member to be joined and the other member to be joined may be metal materials having the same composition or metal materials having different compositions. As the aluminum alloy, a 1000 series alloy, a 2000 series alloy, a 3000 series alloy, a 5000 series alloy, a 6000 series alloy, a 7000 series alloy, or the like is preferably used. Although the shape and dimensions of the members to be joined are not particularly limited, the present invention relates to joining members to be joined having different plate thicknesses, the plate thickness on the thin plate side is 0.8 mm or more, and the plate on the thick plate side The thickness is preferably 4.0 mm or less, and the thickness ratio between the thick plate and the thin plate (thick plate thickness / thin plate thickness) is preferably 2.2 or less. This is because equations (1) to (4) of the present invention are established when the relationship between the plate thickness ratio between the thick plate and the thin plate and the level difference formed above and below is satisfied.
^{_{g 1,2> (f 1,2 / 5}} ) (T / t) 2 -f 1,2 (7)

B. Rotation joining tool As shown in FIG. 1A, a rotation joining tool 3 according to the present invention is provided on a substantially cylindrical upper base 33 and a member to be joined side (lower side in the figure) of the upper base 33. The upper shoulder 32, a substantially cylindrical lower base 35, and a lower shoulder 34 provided on the joined member side (upper side in the drawing) of the lower base 35, and further, the surface of the upper shoulder 32 and the lower shoulder 34 It includes a probe 31 connected between the surface. The probe 31 hangs concentrically with the upper base 33 and the lower base 35. The upper base portion 33, the upper shoulder 32, the lower base portion 35, the lower shoulder 34, and the probe 31 are integrally rotatable.

  The diameters of both shoulders become shorter toward the distal end side, and are maximized at the portions in contact with the upper base portion 33 and the lower base portion 35, respectively. The maximum diameters of these shoulders are equal to the diameters of the base 33 and the lower base 35, respectively. The diameter of the upper base satisfies the above formula (5), and the diameter of the lower base satisfies the above formula (6).

The surfaces of the upper shoulder 32 and the lower shoulder 34 each have a convex curved surface toward the abutting portion. The radius of curvature _{R 1} of the convex curved surface of the upper shoulder 32, satisfies the above formula (1) or (2), the radius of curvature _{R 2} of the convex surface of the lower shoulder 34 satisfies the above expression (3) or (4). In addition, one or more grooves are formed in these convex curved surfaces so as to reach the center from the outer periphery and to allow the members to be joined, which are plasticized by the rotation of the rotary joining tool, to flow into the inside.

  The butted portion between the members to be joined is sandwiched between the upper shoulder and the lower shoulder so that the probe 31 is parallel to the butting surface of the butting portion. The probe 31 moves along the abutting portion while rotating in a state where the upper base portion 33 and the lower base portion 35 are not in contact with the member to be joined.

  The rotary joining tool 3 according to the present invention may have a shape shown in FIG. In the rotary joining tool 3, the upper base 33 includes a main body 330 having a large diameter on the side opposite to the upper shoulder 32. The lower base 35 includes a hexagonal main body 350 on the side opposite to the lower shoulder 34. The upper base portion 33 and the upper shoulder 32 are formed as an integral molded body and can be detached from the main body portion 330 by screwing or the like. Since it is removable, the upper shoulder 32 can be easily cleaned and the probe 31 can be easily attached and detached. Further, by forming the main body 350, the lower base 35, and the lower shoulder 34 as an integral molded body, the integral molded body can be easily detached from the probe 31 with a hexagon wrench. FIG. 1B shows an example in which the upper main body has a large diameter and the lower main body has a hexagonal shape. Alternatively, the upper main body may be hexagonal and the lower main body may have a large diameter. Furthermore, both the main body portions may have a large diameter, or both the main body portions may have a hexagonal shape. Below, the case where the rotary joining tool 3 shown to Fig.1 (a) is used is demonstrated.

  The probe 31 has a substantially cylindrical shape. The probe 31 is connected between the surface of the upper shoulder 32 and the surface of the lower shoulder 34, and is concentric with the upper base portion 33 and the lower base portion 35 from the surface of the upper shoulder 32 toward the surface of the lower shoulder 34. Hang down. The length of the probe 31 is shorter than the plate thickness of the thin plate side member to be joined. The radius of the probe 31 depends on the material of the probe, but is preferably about twice the thickness of the thin plate-side joined member. On the outer peripheral surface of the probe 31, a screw groove may be provided as a stirring blade so that the plasticized member to be joined flows more actively. In order to increase the flow of the plasticized member to be joined, in addition to the thread groove, the probe 31 may be a multiplanar body whose side surfaces are chamfered by about 2 to 4 surfaces. Further, in the case of such a multi-planar body, it is preferable that the direction of the thread groove on each surface where the thread groove is cut alternate with the right screw and the left screw. Such a form is particularly preferable for a bobbin tool using upper and lower shoulders as shown in FIG. Both the shoulders 32 and 34 and the probe 31 are made of a metal material harder than the members to be joined, such as tool steel.

  As shown in FIG. 2, one or more grooves provided on the surfaces of the upper shoulder 32 and the lower shoulder 34 from the outer periphery to the center and so that the material to be joined plasticized by rotation flows into the inside. Are provided. 2A shows that the spiral grooves 36 and 37 of the upper shoulder 32 rotate around the probe 31, and FIG. 2B shows that the spiral grooves 38 and 39 of the lower shoulder 34 extend around the probe 31. In FIG. Shown to rotate. When the rotary joining tool is rotated counterclockwise when used from above the upper base, the spiral grooves 36 and 37 of the upper shoulder 32 are formed clockwise, and the spiral grooves 38 and 39 of the lower shoulder 34 are formed. Are formed counterclockwise. On the contrary, when the rotary joining tool is rotated clockwise when viewed from above the upper base, the spiral grooves 36 and 37 of the upper shoulder 32 are formed counterclockwise, and the lower shoulder 34 is formed. The spiral grooves 38 and 39 are formed clockwise.

As shown in FIG. 3, as the two members to be joined, a thick plate to be joined member 11 (hereinafter simply referred to as “thick plate 11”) and a thin plate to be joined member 12 (thickness t). Hereinafter, simply referred to as “thin plate 12”) is used. The side face of the thick plate 11 and the side face of the thin plate 12 are used as butt surfaces, and butt portions are formed so as to be in close contact with each other. The probe 31 is parallel to the butting surface at the butting portion.
The upper base 33 and the lower base 35 of the rotary joining tool are not in contact with the thick plate 11 and the thin plate 12, and one or more grooves are formed in the upper and lower shoulders 32 and 34, respectively. As a result, the metal plasticized on the thick plate 11 side pushed by the upper and lower shoulders 32 and 34 flows into the groove provided in the upper shoulder 32, and the inside of the groove provided in the lower shoulder 34. Flow into. The joined members that have flown into the inside are prevented from being discharged to the outside as burrs. Further, the upper and lower shoulders 32 and 34 are in contact with the thin plate 12 at a certain area, and are also in contact with the thick plate 11 at the certain area or the entire surface. Thereby, with respect to the thick plate 11 and the thin plate 12 which are to-be-joined members, appropriate heat input can be added from both shoulders. As described above, the grooves provided in the upper and lower shoulders 32 and 34 and the upper and lower shoulders 32 and 34 come into contact with the thick plate 11 and the thin plate 12 with a predetermined area, respectively, so that a tunnel defect or the like occurs at the joint portion. Thus, a poor bonding material can be prevented and a good bonding material can be obtained.

The structure of the rotary joining tool preferably satisfies the above formulas (1) to (4). By satisfying the expressions (1) to (4), as shown in FIG. 3, the upper shoulder 32 and the lower shoulder 34 are in contact with the thin plate 12 side by a certain area, and the upper shoulder 32 and the lower shoulder 34 are also on the thick plate 11 side. The upper base portion 33 and the lower base portion 35 of the rotary joining tool 3 are pushed in without contacting the thick plate 11 and the thin plate 12. In addition, the radius of curvature (R ₁ , R ₂ ) of the convex curved surface for giving an appropriate amount of heat input to the member to be joined can be determined.

The diameter _{D 1} of the upper base portion 33, each of the above formulas the diameter _{D 2} of the lower base part 35 (5), be determined from (6), as shown in FIG. 3, the thickness and the upper and lower shoulder 32, 34 The radii r _L1 and r _L2 of the projection surface of the contact surface of the plate 11 are in a range of 2T <r _L1 <4.5T and 2T <r _L2 <4.5T. Further, the radii r _s1 and r _s2 of the projection surface of the contact surface between the upper and lower shoulders 32 and 34 and the thin plate 12 are in the range of 2t <r _s1 <4.5t and 2t <r _s2 <4.5t. These conditions were obtained by the present inventors based on research and experiment. The thickness of the thin plate 12 is 0.8 mm or more, the thickness of the thick plate 11 is 4.0 mm or less, The thickness ratio of the thin plates (thick plate thickness / thin plate thickness) is preferably 2.2 or less. This is because equations (1) to (4) of the present invention are established when the relationship between the plate thickness ratio between the thick plate and the thin plate and the level difference formed above and below is satisfied.
^{_{g 1,2> (f 1,2 / 5}} ) (T / t) 2 -f 1,2 (7)
Within this range, it is the range of the contact area of the shoulder that enables sound joining. However, it is desirable to set the push-in amounts f ₁ and f ₂ to be 1/10 or less of the plate thickness t of the thin plate 12. An indentation amount exceeding this increases the amount of burrs and decreases the bonding stability.

C. Analysis of Formulas (1) to (6) Detailed explanations of Formulas (1) to (6) are shown below. From FIG. 3, the relationship between r _Ll and R _l is as follows.
R _l cos θ _l = R _l − (g _l + f _l ), R _l sin θ _l = r _Ll
Here, since sin ² θ _l + cos ² θ _l = 1,
^{_{(1 / R l 2) (}} R l -g l -f l) 2 + (r Ll 2 / R l 2) = 1
R _l ² −2R _l (g _l + f _l ) + (g _l + f _l ) ² + r _Ll ² = R _l ^{2
_{R l = [{(g l}} + f l) 2 + r Ll 2} / 2 (g l + f l)] (8)
The relationship between r _sl and R _l is as follows.
_{R l cosψ l = R l -f} l, R l sinψ l = r sl
As before, the following equation is derived.
R _l = (f _l ² + r _sl ² ) / 2f _l (9)

Here, r _Ll and r _sl are obtained experimentally in the relationship between t and T as described above, and 2T ≦ r _Ll ≦ 4.5T and 2t ≦ r _sl ≦ 4.5t. From the above formulas (8) and (9), the following formula is obtained.
[{(G ₁ + f ₁ ) ² + 4T ² } / 2 (g ₁ + f ₁ )] ≦ R ₁ ≦ [{(g ₁ + f ₁ ) ² + 20T ² } / 2 (g ₁ + f ₁ )]
{(F _l ² + 4t ² ) / 2f _l } ≦ R _l ≦ {(f _l ² + 20t ² ) / 2f _l }
Here, since the range satisfying the above two formulas varies depending on the magnitude of g ₁ , it is as follows.
[4t ² −f ₁ ² − {(4t ² −f ₁ ² ) ² + 16f ₁ ² (t ² −T ² )} ^1/2 ] / 2 f ₁ ≦ g ₁ ≦ [4t ² −f ₁ ² + {( 4t ² −f ₁ ² ) ² + 16f ₁ ² (t ² −T ² )} ^1/2 ] / 2f ₁
time,
(F ₁ ² + 4t ² ) / 2f ₁ ≦ R ₁ ≦ {(g ₁ + f ₁ ) ² + 20T ² } / 2 (g ₁ + f ₁ )
(1)
And if outside the above range,
{(G ₁ + f ₁ ) ² + 4T ² } / 2 (g ₁ + f ₁ ) ≦ R ₁ ≦ (f ₁ ² + 20t ² ) / 2f ₁
(2)
Thus, the above formulas (1) and (2) are derived.

When R _l is determined from the above range, as can be seen from FIG. 3, the shoulder diameter is twice r _Ll , and therefore, the following equation (5) is obtained.
^{_{(1 / R l 2) (}} R l -g l -f l) 2 + (r Ll 2 / R l 2) = 1
^{_{r Ll 2 = R l 2 -}} (R l -g l -f l) 2
^{_{r Ll 2 = (2R l -g}} l -f l) (g l + f l)
2r _Ll = 2 {(2R ₁ -g ₁ -f ₁ ) (g ₁ + f ₁ )} ^1/2
Therefore, in order to contact both the plates 11 and 12 with only the convex curved surface of the shoulder when the push amount is f ₁ , the diameter of the base 33 is D ₁ as follows.
D ₁ ≧ 2 {(2R ₁ −g ₁ −f ₁ ) (g ₁ + f ₁ )} ^1/2 (5)

The same applies to the lower shoulder, and the above formulas (3) and (4) are obtained.
[4t ² −f ₂ ² − {(4t ² −f ₂ ² ) ² + 16f ₂ ² (t ² −T ² )} ^1/2 ] / 2f ₂ ≦ g ₂ ≦ [4t ² −f ₂ ² + {( 4t ² −f ₂ ² ) ² + 16f ₂ ² (t ² −T ² )} ^1/2 ] / 2f ₂
time,
(F ₂ ² + 4t ² ) / 2f ₂ ≦ R ₂ ≦ {(g ₂ + f ₂ ) ² + 20T ² } / 2 (g ₂ + f ₂ )
(3)
And if outside the above range,
{(G ₂ + f ₂ ) ² + 4T ² } / 2 (g ₂ + f ₂ ) ≦ R ₂ ≦ (f ₂ ² + 20t ² ) / 2f ₂
(4)
It becomes.
As for the diameter D ₂ of the lower base, as above the base the following equation (6) is obtained.
D ₂ ≧ 2 {(2R ₂ −g ₂ −f ₂ ) (g ₂ + f ₂ )} ^1/2 (6)

D. Grooves formed on the shoulder end surface Further, as shown in FIGS. 2A and 2B, the thick metal and the thin plasticized metal are formed in the grooves 36 and 37 provided in the upper shoulder 32, and the lower shoulder 34, respectively. It is suppressed that it flows into the grooves 38 and 39 provided and is discharged to the outside as burrs. That is, the metal of the thick plate and the thin plate is heated and plasticized by friction with the upper and lower shoulders 32 and 34 during joining, and the upper and lower shoulders 32 and 34 are pushed into the grooves 36, 37 and 38. , 39 flows into each of them, and is appropriately held in the groove and stays at the joining portion. The groove is not limited to the spiral groove as shown in the figure, and may be a non-vortex groove. The spiral groove is not limited to a combination of two Archimedean spiral curves as shown in the figure, but it turns into a gentle curve from the center to the outside, such as a Fermat spiral or involute curve. If it is what. Moreover, you may provide the herringbone groove | channel from which the same effect is acquired. The cross-sectional shape of the groove may be square, U-shaped, semicircular, or the like depending on the tool to be processed, but is not limited thereto. By combining one or more grooves as described above, the metal of the member to be joined that has been plasticized during joining can be effectively retained in the shoulder.

  Next, specific examples of the groove will be described. As described above, the purpose of providing the grooves 36, 37 and 38, 39 is to prevent the plasticized metal pushed out from the thick plate and the thin plate from being ejected as burrs when the shoulder is pushed into the butted portion of the joined member. It is.

First, the volume V _g1 into which the upper shoulder 32 is pushed into the thick plate 11 is obtained based on FIGS. A minute volume dV _{1 (} not shown) is expressed by the following equation.
dV ₁ = (1/2) π {R ₁ ² − (R ₁ −r) ² } dr = (1/2) πr (2R ₁ r−r) dr
Integrate this,
_{V g1 = ∫dV 1 = (1/2} ) ∫πr (2R 1 -r) dr = (1/2) g 1 2 {R 1 - (g 1/3)} is obtained. In this equation, the integration from 0 to g ₁ is performed in the second ∫. _{Incidentally,} represented by _{g 1 + g 2 = T-} t. Here, if the volume of the spiral groove is larger than the V _g1 , the generation of burrs can be prevented.

D-1. In the following, a case where two Archimedean spiral curves are used as a specific example of the spiral groove will be described. The present invention is not limited to this specific example. The spiral grooves 36 and 37 shown in FIG. 2A can be expressed by the following formula based on FIG.
(Vortex groove 36)
_{r l = r p + {(} r s -r p) / 2Nπ} θ ··· spiral groove 36 inner edge curve _{r l '= r p + h} + {(r s -r p) / 2Nπ} θ ··· spiral groove 36 outer edge curve (vortex groove 37)
r ₂ = − [r _p + {(r _s −r _p ) / 2Nπ} θ]...
r ₂ ′ = − [r _p + h + {(r _s −r _p ) / 2Nπ} θ]... spiral groove 37 outer edge curve Here, r _l , r _l ′, r ₂ , r ₂ ′ Not shown. N: number of vortex circumferences, h: groove width, r _s : upper shoulder diameter, r _p : probe diameter.

Moreover, the interval δ between the spiral grooves 36 and 37 shown in FIG.
_{δ = r p + {(r} s -r p) / 2Nπ} 2nπ-r p -h - {(r s -r p) / 2Nπ} (2n-1) π = {(r s -r p) / 2N} -h
r _s −r _p = 2N (δ + h)
_{N = {(r s -r p} ) / 2 (δ + h)} (10)
N is an arbitrary integer, and 0 <n ≦ N.
Here, since the spiral grooves 34 and 35 have the same shape, the minute area dS of both spiral grooves is as follows.
dS = 2 × (1/2) (r _l ′ ² dθ−r _l ² dθ) = {(r _l + h) ² −r _l ² } dθ = h (2r _l + h) dθ
Here, when the depth of the spiral groove is d ₀ , the volume V of the groove is as follows.
V = d ₀ ∫ds = d ₀ ∫h (2r ₁ + h) dθ = d ₀ h ∫ [2r _p + {(r _s −r _p ) / Nπ} θ + h] dθ = d ₀ h [2r _p θ + hθ + {( r _s −r _p ) / 2Nπ} θ ² ] = 2d ₀ hNπ (2r _p + h + r _s −r _p ) = 2d ₀ hNπ (r _s + r _p + h), where all integration ranges from 0 to 2Nπ is there.

Therefore, the rotary tool is such that the volume V to be involved in spiral groove is greater than V _g1 when one rotation, when V> V _{g1,
^{d 0> {g 1 2 (}} 3R 1 -g 1)} / {12hN (r s + r p + h)} (11)
Thus, using equations (10) and (11), it is possible to select a groove that allows actual processing. In actual processing, considering the cost and the like, the groove width and interval are h ≧ 0.5 mm and δ ≧ 0.5 mm. From the equation (10), h, δ, N is determined, and the groove depth d ₀ is determined from the equation (11).
However, d ₀ at this time is also limited in cost and the like in actual processing, and h, δ, and N are determined within a range satisfying the equation (10) so that d ₀ satisfies the range. The spiral grooves 36 and 37 shown in FIG. 2A are clockwise, but may be counterclockwise in determining the groove dimensions. The same applies to the grooves 38 and 39 of the lower shoulder 34.

D-2. Next, let us examine the spiral of Fermat's spiral. Fermat's spiral curve is expressed by the following equation.
(Vortex groove 36)
^{_{r l = (r s 2 θ}} / 2Nπ) 1/2 ··· spiral groove 36 inner curve ^{_{r l '= (r s 2}} θ / 2Nπ) 1/2 + h ··· spiral groove 36 outer curve (spiral groove 37 )
^{_{r 2 = - (r s 2}} θ / 2Nπ) 1/2 ··· spiral groove 37 inner edge curve ^{_{r 2 '= - (r s}} 2 θ / 2Nπ) 1/2 -h ··· spiral groove 37 outer curve here _{in, r l, r l ',} r 2, r 2', N, h, r s is the same as for the above Archimedes spiral curve.

The interval δ between the spiral grooves 1 and 2 is expressed by the following formula.
^{_{δ = (r s 2 (n}} + π) / 2Nπ) 1/2 - (r s 2 n / 2Nπ) 1/2 -h
Here, n is an arbitrary integer, and 0 <n ≦ N. In these spiral grooves, the interval δ between the spiral grooves 34 and 35 is not constant and narrows toward the outside, so that δ> 0 when n + π = 2Nπ.
^{_{h ≦ (r s 2 / 2Nπ}} ) 1/2 {(2Nπ) 1/2 - (2 (N-1) π) 1/2} (12)
It becomes. Further, as in the Archimedean spiral, the microscopic area dS of the spiral groove is expressed by the following equation.
dS = 2 × (1/2) (r _l ′ ² dθ−r _l ² dθ) = {(r _l + h) ² −r _l ² } dθ = h (2r _l + h) dθ
Similarly, the volume V of the groove when the depth of the spiral grooves and d ₀ is as follows.
_{V = d 0 ∫ds = d 0} ∫h (2r l + h) dθ = d 0 h∫ {(r s 2 θ / Nπ) 1/2 + h} dθ = d 0 h [{(2r s 2 / Nπ) ^1/2 } {(2/3) θ ^3/2 } + hθ] = d ₀ h {(8/3) Nπr _s + 2Nπh} = (2/3) d ₀ hNπ (4r + 3h), all integrated in this equation The range is from 0 to 2Nπ.

Thus, as the volume V of the rotational tool is involved in spiral grooves when one rotation is greater than V _g1, When V> V _{g1,
^{d 0> {g 1 2 (}} 3R 1 -g 1)} / {2hN (4r s + 3h)} (13)
Thus, using equations (12) and (13), it is possible to select a groove that allows actual processing. In actual processing, the groove widths are h ≧ 0.5 mm and δ ≧ 0.5 mm in consideration of cost and the like, and h, δ, and N are set so that the number of turns N is 1 or more from the equation (12). The groove depth d ₀ is determined from the equation (13).
However, d ₀ at this time is also limited in cost and the like in actual processing, and h, δ, and N are determined within a range satisfying Expression (12) so that d ₀ satisfies the range. The spiral grooves 36 and 37 shown in FIG. 2A are clockwise, but may be counterclockwise in determining the groove dimensions. The same applies to the grooves 38 and 39 of the lower shoulder 34.

E. Friction stir welding method Next, the friction stir welding method according to the present invention will be described. Here, the case where it joins to the plate-shaped member from which plate | board thickness differs, and is joined together is demonstrated.

As shown in FIG. 5, a thick plate 11 and a thin plate 12 are prepared as two members to be joined. The abutting portions J are formed by butting so that the butting surfaces 11a and 12a are in close contact with each other. Both plate members are fixed so as not to move during joining by a clamp (not shown) or the like so that arbitrary steps g ₁ and g ₂ are formed on the front and back surfaces, respectively.

  As shown in FIG. 6, while rotating the rotary joining tool 3 in the direction of the arrow in the figure, the tool is advanced in the direction of the arrow in the figure, and as shown in FIG. The probe 31 of the rotary joining tool 3 is advanced from the end, and the upper shoulder 32 and the lower shoulder 34 are pressed against the thick plate 11 and the thin plate 12 of the butted portion J. At this time, the probe 31 is inserted in parallel with the abutting surfaces 11a and 12a.

  Thereafter, as shown in FIG. 8, the rotary joining tool 3 is moved in the joining direction indicated by the arrow in the figure. The thin plate 12 is moved to the side (advance side) where the rotation direction of the rotary joining tool 3 coincides with the joining direction (forward side) so that the thick plate 11 is on the opposite side (retreat side). The upper shoulder 32 and the lower shoulder 34 are in contact with the thick plate 11 and the thin plate 12 in a rotated state. Thereby, the thick plate 11 and the thin plate 12 are heated and softened, and plastically flow. The plastic fluidized metal is sandwiched from above and below by the convex curved surfaces of both shoulders 32 and 34, and is prevented from scattering to the outside. Further, the probe 31 plays a role of agitating both the plate materials while plastically flowing both the plate materials by contacting the thick plate 11 and the thin plate 12 in a rotated state. In this manner, the butted portion J of the thick plate 11 and the thin plate 12 is friction stir welded. Next, as shown in FIG. 9, after the friction stir welding is performed over the entire length of the joining length, the rotary joining tool 3 is pushed out from the end of the abutting portion J of the thick plate 11 and the thin plate 12 as it proceeds in the same direction. The friction stir welding process is terminated, and a joint is formed. 6-9 is the thing of Fig.1 (a).

  The rotational speed of the rotary joining tool 3 is set according to the size and shape of the rotary joining tool 3, the material of the thick plate 11 and the thin plate 12, and the plate thickness. In many cases, the rotational speed is 500 rpm to 3000 rpm. Set by range.

  According to the friction stir welding according to the present invention, the thick plate 11 is disposed on the backward side, the thin plate 12 is disposed on the forward side, and the plate thickness is provided without providing pressure adjusting devices inside the upper and lower shoulders of the rotary joining tool 3. Thus, it is possible to friction stir weld the thick plate 11 and the thin plate 12 different from each other, and a good differential thickness joining member can be obtained by a simple method.

  In addition, this invention is not limited to said embodiment, A various deformation | transformation is possible. For example, the thick plate 11 may be arranged on the advance side where the rotation direction of the rotary joining tool coincides with the joining direction, and the thin plate 12 may be arranged on the retreat side which is the opposite side. However, in this case, the amount of burrs generated may increase.

  Moreover, in the said embodiment, although the board | plate material was used as a to-be-joined member, it is also possible to join the extrusion materials which have the level | step difference curved on the surface in the butt | matching part. Even in this case, the friction stir welding method according to the present invention can be carried out using the rotary welding tool for friction stir welding according to the present invention.

  Compared with the conventional method as shown in FIG. 10, in the bobbin type friction stir welding method according to the present invention, a pressure adjusting device that varies the shoulder surface up and down inside the upper and lower shoulders of the rotary welding tool is used. There is no need to provide it. Since the parameters of the joining conditions are the same as those of a normal bobbin type friction stir welding, it is not necessary to control the pressure adjusting device inside the shoulder. Furthermore, the design of the rotary joining tool is simple.

  Further, the convex curved surface of the rotary joining tool can be brought into contact with each of the thick plate and the thin plate in an arbitrary area. As a result, it is possible to give an appropriate amount of heat input to each of the thick plate and the thin plate, and it is possible to perform good bonding without a complicated mechanism as in the conventional method.

  The tailored blank plate material joined by the bobbin type friction stir welding method according to the present invention has a thick plate and a thin plate made of various metals along the abutting surface, and has unjoined portions, tunnel defects such as voids, and the like. It is firmly joined by no healthy and good joints. Therefore, by using it as a tailored blank plate material for automobiles, it is possible to reduce the weight while ensuring sufficient rigidity, and it is possible to effectively suppress the generation of waste during molding.

  Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples, but the present invention is not limited thereto.

Examples 1-9
An aluminum alloy A6022-T4 plate material having a thickness of 2.0 mm was used as a thick plate of the members to be joined, and an aluminum alloy A6022-T4 plate material having a thickness of 1.0 mm was used as a thin plate. These plate materials were bonded by a differential thickness by a bobbin type friction stir welding method. The tensile strength of the A6022-T4 plate material used as the base material was 236 MPa as measured according to JIS Z 2241.

First, in the combination of a plate thickness of 2.0 mm and a thin plate of 1.0 mm, the ranges of the curvature radius R _{1 of} the upper shoulder surface and the curvature radius R ₂ of the lower shoulder surface were determined from the above formulas (1) to (4). Here, the plate thickness T = 2.0 mm on the thick plate side, the step g _{1 of the} butt surface on the upper base side = 1.0 mm, and the step g _{2 of the} butt surface on the lower base side = 0.0 mm Assuming that f ₁ = f ₂ = 0.1 mm so that the amounts f ₁ and f ₂ are 1/10 of the thickness on the thin plate side, the range in which equations (1) and (3) are satisfied is 0.3 ≦ g _{Since 1.2} ≦ 39.6, the range of R ₁ and R ₂ is 20.1 ≦ R ₁ ≦ 36.9, 80.1 ≦ R ₂ ≦ 100.1 from the formulas (1) and (4). It becomes.

In the embodiment, as the curvature radius R ₁ of the upper shoulder surface, three types of R ₁ = 21, 28, and 36 mm within the above range, and as the curvature radius R ₂ of the lower shoulder surface, three types of the radius within the above range. A rotary joining tool having a shoulder convex curved surface of R ₂ = 81, 90, 100 mm was used. When the diameter D _{1 of} the upper base and the diameter D _{2 of the} lower base at each radius of curvature are calculated from the above formulas (5) and (6), the upper base diameter D ₁ ≧ 13.4 corresponding to each R ₁ above. , 15.5 and 17.7 mm. Further, corresponding to each R ₂ described above, the lower base diameter D ₂ ≧ 8.1, 8.5, 8.9 mm. Accordingly, D ₁ = 14, 16, and 18 mm corresponding to each R ₁ , and D ₂ = 9 mm for all R ₂ .

The above-mentioned Archimedes curve was used for the groove provided in the shoulder. The probe radius was r _p = 2.0 mm which is twice the thickness of the thin plate. Two spiral grooves each having an Archimedean curve are provided. When R ₁ = 21, 28, 36 mm and R ₂ = 81, 90, 100 mm, r _s = D / 2 and r _p = 2.0 mm. Calculate for each vortex shape.
In the case of R ₁ = 21 mm, the groove width h is set to three conditions of h = 0.7, 1.0, and 2.0 mm, and the number of turns of each groove is set to 2.0, 1.5, and 1.0. When the groove spacing under these conditions was calculated from the equation (10), all of them were 0.5 mm or more, and it was confirmed that there was no problem in actual processing. Further, when the groove depth d ₀ of each condition was calculated from the equation (11), d ₀ > 0.38, 0.34, 0.24 mm, and d ₀ = 0.4 mm.
In the case of R ₁ = 28 mm, the groove width h is set to three conditions of h = 0.7, 1.0, and 1.5 mm, and the number of turns of each groove is set to 2.0, 1.5, and 1.0. When the groove spacing under these conditions was calculated from the equation (10), it was confirmed that there was no problem with all of 0.5 mm or more. Next, when the groove depth d ₀ was calculated from the equation (11), d ₀ > 0.46, 0.42, and 0.40 mm were obtained, and all were determined to be d ₀ = 0.5 mm.
In the case of R ₁ = 36 mm, the groove width h is set to three conditions of h = 0.5, 0.8, and 1.0 mm, and the number of rounds of each groove is set to 2.5, 2.0, and 1.5. When the groove spacing under these conditions was calculated from the equation (10), all of them were 0.5 mm or more, and it was confirmed that there was no problem. Next, when the groove depth d ₀ is calculated from the equation (11), d ₀ > 0.62, 0.47, 0.5 mm are obtained, and d ₀ = 0.7, 0.5, 0.6 mm are determined, respectively. .
In the case of R ₂ = 81 mm, the groove width h is set to h = 0.5 mm and the number of groove circumferences is set to 1.0. When the groove interval at this time was calculated from the equation (10), it was 0.5 mm or more, and it was confirmed that there was no problem. Next, when the groove depth d ₀ is calculated from the equation (11), d ₀ > 0. Therefore, it was determined that all d ₀ = 0.25 mm.
In the case of R ₂ = 90 mm, the groove width h is set to h = 0.5 mm and the number of groove circumferences is set to 1.0. When the groove spacing under this condition is calculated from Equation (10), there is no problem with all of 0.5 mm or more. When the groove depth d ₀ was calculated from the equation (11), all d ₀ > 0, and therefore all d ₀ = 0.25 mm were determined.
In the case of R ₂ = 100 mm, the groove width h is set to h = 0.5 mm and the number of groove circumferences is set to 1.0. When the groove spacing under this condition is calculated from Equation (10), there is no problem with all of 0.5 mm or more. When the groove depth d ₀ was calculated from the equation (11), all d ₀ > 0, and therefore all d ₀ = 0.25 mm were determined.
Hereinafter, the rotational joining tools combining the upper shoulder and the lower shoulder having these curvature radii are referred to as rotational joining tools 1 to 9. The combinations in each example are summarized in Table 1.

  The side surface of the probe was cut by 0.5 mm every 90 °, the four surfaces were flat, and the other surface was threaded to form a substantially octagon (eight surfaces). The direction of the screw on each surface was alternately right and left. The length of the probe was 0.8 mm obtained by subtracting the pushing amount of the upper shoulder and the lower shoulder from the thickness of the thin plate.

  The thick plate and the thin plate to be joined were cut to a width of 150 mm and a length of 400 mm, and the long sides were butt-joined so that the shape after the butt was 300 mm wide and 400 mm long.

  Using the above nine types of rotary joining tools 1 to 9, the thick plate and the thin plate were subjected to friction stir welding under the conditions of a rotational speed of 1500 rpm and a joining speed of 700 mm / min. During the joining, the rotary joining tool is not tilted on either side of the two plate materials nor in the front-rear direction of the joining direction. Further, the rotary welding tool is rotated counterclockwise as viewed from above, and a thin plate is placed on the side where the rotational direction of the rotary welding tool coincides with the joining direction (advance side), and the side on which the welding direction is opposite to that of the rotary welding tool ( A thick plate was placed on the retreat side.

  In order to measure the joint strength of the joint material thus friction stir welded, a JIS No. 5 type test piece was cut out from each joint material and used as a sample. This sample was cut so that the joining line was positioned at the center of the test piece and the tensile direction in the tensile test was perpendicular to the joining line. About each test piece, the tensile test was done according to JISZ2241 at normal temperature, and the tensile strength was measured. This tensile strength was defined as joint strength. The ratio of joint strength to base material strength was defined as joint efficiency. Table 4 shows the joint strength and joint efficiency.

Comparative Examples 1-9
The same thick plate and thin plate as used in Examples 1 to 9 were used as the members to be joined, and a friction stir welding test was performed using the following nine types of rotary joining tools different from the examples.

As described above, the ranges of R ₁ and R ₂ obtained from the above formulas (1) to (4) are 20.1 ≦ R ₁ ≦ 36.9 and 80.1 ≦ R ₂ ≦ 100.1. As a comparative example, rotary joint tools 10 to 13 in which the curvature radius R ₁ of the convex curved surface of the upper shoulder and the curvature radius R ₂ = 40 mm and 150 mm of the convex curved surface of the lower shoulder, which are outside this range, were used. (Comparative Examples 1-4).

When the diameters D ₁ and D ₂ of the upper base and the lower base at the respective radii of curvature are calculated from the above formulas (5) and (6), the upper base diameter D ₁ > 11.3 when R ₁ = 15 mm. _{Since 1} = 12 mm and R ₁ = 40 mm, the upper base diameter D ₁ > 18.6, so D ₁ = 20 mm. Further, since the diameter D ₂ > 5.7 of the lower base is R ₂ = 40 mm, D ₂ = 8 mm, and the diameter D ₂ > 10.9 of the lower base is R ₂ = 150 mm, so D ₂ = 12 mm. It was.

In addition comparative examples 5 to _8, R 1, for _{R 2} satisfies the above range _{R 1, R 2 (20.1 ≦} R 1 ≦ 36.9,80.1 ≦ R 2 ≦ 100.1) R 1 = 21, 36 mm, R ₂ = 81, 100 mm, but the diameters D ₁ and D _{2 of} the upper base and the lower base are D ₁ = 12 mm, 16 mm, D ₂ = 8 mm, and 8 mm, respectively. The rotary joining tools 14 to 17 that do not satisfy (6) were used. The combinations in each comparative example are summarized in Table 1.

An Archimedean curve was used for the groove provided in the shoulder, as in the example. Two spiral grooves each having an Archimedean curve were provided, and in the rotary joining tools 10 to 17, r _s = D / 2 and r _p = 2.0 mm. Here, when R ₁ = 15 mm and D ₁ = 12 mm, the groove width h = 1.0 mm and the number of turns N = 1, and the groove interval δ is calculated from the equation (10), δ = 1.0 mm, In the case of R ₁ = 40 mm and D ₁ = 20 mm, if the groove width is h = 1.0 mm and the number of turns is N = 2.0, then δ = 1.0 mm, and there is no problem in actual tool processing. It could be confirmed. Further, when the groove depth d ₀ is calculated from the equation (11), when R ₁ = 15 mm and D ₁ = 12 mm, d ₀ > 0.41 mm, and when R ₁ = 40 mm and D ₁ = 20 mm Since d ₀ > 0.38 mm, both were determined to be d ₀ = 0.5 mm.

On the other hand, when R ₂ = 40 mm and D ₂ = 8 mm, assuming that the groove width is h = 0.5 mm and the number of turns is N = 1, the groove interval δ is calculated from the equation (10), then δ = 0.5 mm, When R ₂ = 150 mm and D ₂ = 12 mm, assuming that the groove width is h = 1.0 mm and the number of turns is N = 1.0, δ = 1.0 mm, and there is no problem in actual tool processing. It could be confirmed. Further, when the depth d _{0 of the} groove is calculated from the equation (11), d ₀ > ₀ mm in both cases of R ₂ = 40 mm and D ₂ = 8 mm and R ₂ = 150 mm and D ₂ = 12 mm. Both were determined to be d ₀ = 0.25 mm.

Further, when R ₁ = 21 mm and D ₁ = 12 mm, the groove width h = 1.0 mm, the number of turns N = 1, and the groove interval δ is calculated from the equation (10), then δ = 1.0 mm, R _{In the case of 1} = 36 mm and D ₁ = 16 mm, if the groove width is h = 1.5 mm and the number of turns is N = 1, δ = 1.5 mm, and it was confirmed that there is no problem in the actual tool processing. . Further, when the depth d _{0 of the} groove is calculated from the equation (11), when R ₁ = 21 mm and D ₁ = 12 mm, d ₀ > 0.57 mm, and when R ₁ = 36 mm and D ₁ = 16 mm Since d ₀ > 0.52 mm, both were determined as d ₀ = 0.6 mm.

On the other hand, when R ₂ = 81 mm and D ₂ = 8 mm, the groove width δ is calculated from Equation (10) with the groove width h = 0.5 mm and the number of turns N = 1.0. Even when R ₂ = 100 mm and D ₂ = 8 mm, if the groove width is h = 0.5 mm and the number of turns is N = 1.0, then δ = 0.5 mm, and there is no problem in actual tool processing. I was able to confirm. Further, when the groove depth d ₀ is calculated from the equation (11), when R ₂ = 81 mm, D ₂ = 8 mm, R ₂ = 100 mm, and D ₂ = 8 mm, both are d ₀ > ₀ mm. From the above, it was determined that d ₀ = 0.25 mm.

Furthermore, in Comparative Example 9, the ranges of R ₁ and R ₂ obtained from the above formulas (1) to (4) (20.1 ≦ R ₁ ≦ 36.9, 80.1 ≦ R ₂ ≦ 100.1) are satisfied. In addition, a rotary joining tool 18 satisfying the above formulas (5) and (6), R ₁ = 21 mm and D ₁ = 14 mm, R ₂ = 81 mm and D ₂ = 9 mm, and no groove on both shoulder surfaces is provided. Using.

  The friction stir welding tests of Comparative Examples 1 to 9 were performed under the same conditions as in Examples 1 to 9. About the obtained joining material, it carried out similarly to Examples 1-9, the joint strength was measured, and the joint efficiency was calculated | required. The results are shown in Table 4.

  As is apparent from Table 4, in Examples 1 to 9, the joint strength was almost the same as the base material strength, and both fractured on the thin plate side, resulting in a joint efficiency of 98% or more and a high strength joining material. Thus, it became clear that the member to be joined that was joined using the rotary joining tool having the shoulder structure defined in the present invention has good joint characteristics.

  On the other hand, in all of Comparative Examples 1 to 9, the joint efficiency was 95% or less, and fracture occurred at the base material or the joint on the thin plate side, and a high-strength joint material was not obtained.

Specifically, in Comparative Example 1, since the curvature radii of the convex curves of the upper shoulder and the lower shoulder were both too small, heat input to the thin plate material and the thick plate material was insufficient. As a result, internal defects occurred and the joint strength was poor.
In Comparative Example 2, the heat input from the upper shoulder is insufficient because the radius of curvature of the convex curve of the upper shoulder is too small, and the heat input from the lower shoulder is excessive because the radius of curvature of the convex curve of the lower shoulder is too large. It was. As a result, the heat input balance from the upper and lower shoulders was lacking, internal defects were generated, and the joint strength was inferior.
On the other hand, in Comparative Example 3, the heat input from the upper shoulder is excessive because the curvature radius of the convex curve of the upper shoulder is too large, and the heat input from the lower shoulder is too small because the curvature radius of the convex curve of the lower shoulder is too small. I was short. As a result, the heat input balance from the upper and lower shoulders was lacking, internal defects were generated, and the joint strength was inferior.
In Comparative Example 4, since the curvature radii of the convex curves of the upper shoulder and the lower shoulder were both too large, heat input to the thin plate material and the thick plate material was excessive. As a result, the heat-affected zone became large and the joint strength was inferior.
In Comparative Examples 5 to 8, since the diameters of the upper base and the lower base were too small with respect to the indentation amount, the plate thickness, and the radius of curvature, the base contacted the thick plate and many burrs were generated. As a result, the flow of the member to be joined to the joined portion was insufficient, and the plate thickness at the joined portion was reduced, resulting in poor joint strength.
In Comparative Example 9, since the spiral grooves were not formed on the convex curved surfaces of the upper and lower shoulders, all the members to be joined extruded by both shoulders became burrs. As a result, the joint thickness was inferior because the plate thickness at the joint decreased.

Examples 10-18
An aluminum alloy A5182-O plate material having a thickness of 1.7 mm was used as the thick plate of the members to be joined, and an aluminum alloy A5182-O plate thickness of 0.8 mm was used as the thin plate. These plate materials were joined by a thickness difference by a bobbin type friction stir welding method. The tensile strength of the A5182-O plate used as the base material is JIS
It was 274 MPa when measured according to Z 2241.

First, in the combination of a plate thickness of 1.7 mm and a thin plate of 0.8 mm, the ranges of the curvature radius R _{1 of} the upper shoulder surface and the curvature radius R ₂ of the lower shoulder surface were determined from the above formulas (1) to (4). Here, the plate thickness T on the thick plate side is 1.7 mm, the step g ₁ on the butt surface on the upper base side, and the step on the butt surface on the lower base side are g ₁ = 0.9 mm, g ₂ = 0 mm, and indentation, respectively. When the amounts f ₁ and f ₂ are both 1/10 or less of the thickness on the thin plate side and f ₁ = f ₂ = 0.08 mm, the range in which the expressions (1) and (3) are satisfied is 0.3 ≦ g _{1 , 2} ≦ 31.6, the range of R ₁ and R ₂ is 16.0 ≦ R ₁ ≦ 30.0, 72.3 ≦ R ₂ ≦ 80.0 from the formulas (1) and (4). Become.

In the embodiment, as the curvature radius R ₁ of the upper shoulder surface, three kinds of R ₁ = 17, 23, 29 mm within the above range, and as the curvature radius R ₂ of the lower shoulder surface, three kinds of curvature within the above range. A rotary joining tool having a shoulder convex curved surface of R ₂ = 73, 76, 80 mm was used. When the diameter D _{1 of} the upper base and the diameter D _{2 of the} lower base at each curvature radius are calculated from the above formulas (5) and (6), the upper base diameter D ₁ ≧ 11.4 corresponding to each R _1. 13.3 and 15.0 mm. Similarly, each R ₂ has a lower base diameter D ₂ ≧ 6.8, 7.0, 7.2 mm. Thus, D ₁ = 12, 14, 16 mm and D ₂ were all set to D ₂ = 8.0 mm corresponding to the above R ₁ and R ₂ .

The above-mentioned Archimedes curve was used for the groove provided in the shoulder. The probe radius was r _p = 1.6 mm which is twice the thickness of the thin plate. Two spiral grooves composed of Archimedean curves are provided, and calculation is performed for each spiral shape.
In the case of R ₁ = 17 mm, the groove width h is set to three conditions of h = 0.5, 1.0, and 1.5 mm, and the number of turns of each groove is set to 2.0, 1.4, and 1.0. When the groove interval under these conditions was calculated from the equation (10), all of them were 0.5 mm or more, and it was confirmed that there was no problem. Next, when the groove depth d ₀ was calculated from the equation (11), d ₀ > 0.42, 0.28, 0.25 mm, and d ₀ = 0.5, 0.4, 0.3 mm, respectively.
In the case of R ₁ = 23 mm, the groove width is set to three conditions of h = 0.5, 1.0, and 1.5 mm, and the number of rounds of each groove is set to 2.5, 1.5, and 1.0. When the groove spacing under these conditions was calculated from the equation (10), all of them were 0.5 mm or more, and it was confirmed that there was no problem. Next, when the groove depth d ₀ was calculated from the equation (11), d ₀ > 0.40, 0.32, and 0.30 mm were obtained, and all were determined to be d ₀ = 0.5 mm.
In the case of R ₁ = 29 mm, the groove width h is set to three conditions of h = 1.0, 1.5, and 2.0 mm, and the number of turns of each groove is set to 2.0, 1.5, and 1.0. When the groove spacing under these conditions was calculated from the equation (10), all of them were 0.5 mm or more, and it was confirmed that there was no problem. Next, when the groove depth d ₀ was calculated from the equation (11), d ₀ > 0.27, 0.23, and 0.25 mm were obtained, and all were determined to be d ₀ = 0.3 mm.

When R ₂ = 73 mm, the groove width h was set to h = 0.5 mm, and the number of turns was set to 1.0. When the groove interval under this condition was calculated from the equation (10), it was confirmed that there was no problem with 0.5 mm or more. Next, when the groove depth d ₀ was calculated from the equation (11), d ₀ > 0 and all were determined as d ₀ = 0.25 mm.
Similarly, in the case of R ₂ = 76, 80 mm, the groove width h was set to h = 0.5 mm, and the number of turns was set to 1.0. As with the previous case, there is no problem with the groove spacing. Similarly, all the groove depths were determined to be d ₀ = 0.25 mm. The combinations in each example are summarized in Table 2.

  The side surface of the probe was cut by 0.5 mm every 90 ° to make four surfaces flat, and the other surface was cut into screw grooves to form a substantially octagon (eight surfaces). The direction of the screw on each surface was alternately right and left. The length of the probe was 0.64 mm obtained by subtracting the pushing amount of the upper shoulder and the lower shoulder from the thickness of the thin plate.

  The thick plate and the thin plate to be joined were cut into a width of 150 mm and a length of 400 mm, and the long sides were butt-joined so that the shape after the butt was 300 mm wide and 400 mm long.

  Using the above nine types of rotary joining tools 19 to 27, the thick plate and the thin plate were subjected to friction stir welding under the conditions of rotational speed: 1000 rpm and joining speed: 300 mm / min. During the joining, the rotary joining tool is not tilted on either side of the two plate materials nor in the front-rear direction of the joining direction. The rotary welding tool is rotated counterclockwise when viewed from above, and a thin plate is placed on the side where the rotational direction of the rotary welding tool coincides with the welding direction (advance side), and the rotational direction of the rotary welding tool is opposite to the welding direction. A thick plate was placed on the side (retreat side).

In order to measure the joint strength of the joint material friction-stir welded in this way,
A No. 5 type test piece was cut out and used as a sample. This sample was cut so that the joining line was positioned at the center of the test piece and the tensile direction in the tensile test was perpendicular to the joining line. About each test piece at room temperature, JIS
A tensile test was performed according to Z2241, and the tensile strength was measured. This tensile strength was defined as joint strength. The ratio of joint strength to base material strength was defined as joint efficiency. Table 5 shows the joint strength and joint efficiency.

Comparative Examples 10-15
The same thick plate and thin plate as those used in Examples 10 to 15 were used as members to be joined, and a friction stir welding test was performed using the following six types of rotary joining tools different from the examples.

As described above, the ranges of R ₁ and R ₂ obtained from the above formulas (1) to (4) are 16.0 ≦ R ₁ ≦ 30.0 and 72.3 ≦ R ₂ ≦ 80.0. As a comparative example, rotational joint tools 28 to 31 in which the curvature radius R ₁ of the convex curved surface of the upper shoulder outside this range is 14 mm and 40 mm, and the curvature radius R ₂ of the convex curved surface of the lower shoulder is similarly 65 mm and 90 mm are combined. Used (Comparative Examples 10 to 13). Since the diameters of the respective bases are D ₁ ≧ 10.3 mm, 17.6 mm, D ₂ ≧ 6.4 mm, and 7.6 mm, D ₁ = 12 mm, 18 mm, D ₂ = 7.2 mm, and 8.0 mm, respectively. did.

Furthermore, in Comparative Example 14, R ₁ and R ₂ satisfy R ₁ = 23 mm satisfying the above R ₁ and R ₂ ranges (16.0 ≦ R ₁ ≦ 30.0, 72.3 ≦ R ₂ ≦ 80.0). R ₂ = 76 mm, but the diameters D ₁ and D _{2 of} the upper base portion and the lower base portion are D ₁ = 12 mm and D ₂ = 6.0 mm, respectively, and do not satisfy the above formulas (5) and (6) 32 was used. The combinations in each comparative example are summarized in Table 2.

An Archimedean curve was used for the groove provided in the shoulder, as in the example. The probe radius was r _p = 1.6 mm which is twice the thickness of the thin plate. Two spiral grooves composed of Archimedean curves are provided, and the respective vortex shapes of the rotary joining tools 28 to 31 are calculated.
In the case of R ₁ = 14 mm, the groove width h is set to two conditions of h = 0.9 and 1.5 mm, and the number of rounds of each groove is set to 1.5 and 1.0. When the groove interval under these conditions was calculated from the equation (10), all of them were 0.5 mm or more, and it was confirmed that there was no problem. Next, when the groove depth d ₀ was calculated from the equation (11), d ₀ > 0.24 and 0.20 mm, respectively, and d ₀ = 0.3 mm in both cases.
In the case of R ₁ = 40 mm, the groove width h is set to two conditions of h = 1.0 and 2.0 mm, and the number of rounds of each groove is set to 2.0 and 1.0. When the groove interval under these conditions was calculated from the equation (10), all of them were 0.5 mm or more, and it was confirmed that there was no problem. Next, when the groove depth d ₀ was calculated from the equation (11), d ₀ > 0.35 and 0.32 mm, respectively, and all were determined to be 0.4 mm.
In the case of R ₂ = 65 mm, the groove width h is set to h = 0.5 mm and the number of groove circumferences is set to 1.0. When the groove spacing under this condition was calculated from the equation (10), it was confirmed that there was no problem at 0.5 mm or more. When the groove depth d ₀ was determined from the equation (11), d ₀ > ₀ mm was obtained, which was determined to be 0.3 mm.

In the case of R ₂ = 90 mm, the groove width h is set to h = 0.5 mm and the number of groove circumferences is set to 1.0. When the groove spacing under this condition was calculated from Equation (10), it was confirmed that there was no problem with 0.5 mm or more. When the groove depth d ₀ was determined from the equation (11), d ₀ > ₀ mm was obtained, which was determined to be 0.3 mm.
In the case of R ₁ = 23 mm and D ₁ = 12 mm, the groove width h is set to h = 1.0 mm, and the number of groove turns is set to N = 1. When the groove interval under this condition is calculated from the equation (10), it is 0.5 mm or more, and there is no problem in processing. Further, when the groove depth d ₀ was calculated from the equation (11), it was determined that d ₀ > 0.53 mm and d ₀ = 0.6 mm.
Further, in the case of R ₂ = 76 mm and D ₂ = 6.0 mm, the groove width h is set to h = 0.5 mm, and the number of circulations of the groove is set to N = 0.7. When the groove spacing under this condition is calculated from Equation (10), it can be confirmed that there is no problem with 0.5 mm or more. When the groove depth d ₀ was obtained from the equation (11), d ₀ > 0 and d ₀ = 0.25 mm was determined.

Further, in Comparative Example 15, the ranges of R ₁ and R ₂ obtained from the above formulas (1) to (4) (16.0 ≦ R ₁ ≦ 30.0, 72.3 ≦ R ₂ ≦ 80.0) are satisfied. In addition, R ₁ = 23 mm, D ₁ = 14 mm, R ₂ = 76 mm, D ₂ = 8.0 mm satisfying the above formulas (5) and (6), and grooves are not provided on both shoulder surfaces 33 was used.
The combinations in each comparative example are summarized in Table 2.

  Under the same conditions as in Examples 10 to 18, friction stir welding of Comparative Examples 10 to 15 was performed. About the obtained joining material, it carried out similarly to Examples 10-18, and joint strength was measured and joint efficiency was calculated | required. The results are shown in Table 5.

  As is apparent from Table 5, in Examples 10 to 18, the joint strength was the same as the base material strength, and both fractured on the thin plate side, the joint efficiency was 100%, and a high-strength joining material was obtained. Thus, it became clear that the members to be joined that were joined using the rotary joining tool having the shoulder structure defined in the present invention have good joint characteristics.

  On the other hand, in all of Comparative Examples 10 to 15, the joint efficiency was 93% or less, and fracture occurred at the base material or the joint on the thin plate side, and a high-strength joint material was not obtained.

Specifically, in Comparative Example 10, since the curvature radii of the convex curves of the upper shoulder and the lower shoulder were both too small, heat input to the thin plate material and the thick plate material became insufficient. As a result, internal defects occurred and the joint strength was poor.
In Comparative Example 11, the heat input from the upper shoulder is insufficient because the curvature radius of the convex surface of the upper shoulder is too small, and the heat input from the lower shoulder is excessive because the curvature radius of the convex curve of the lower shoulder is too large. It was. As a result, the heat input balance from the upper and lower shoulders was lacking, internal defects were generated, and the joint strength was inferior.
On the other hand, in Comparative Example 12, the heat input from the upper shoulder is excessive because the curvature radius of the convex curve of the upper shoulder is too large, and the heat input from the lower shoulder is excessive because the curvature radius of the convex curve of the lower shoulder is too small. I was short. As a result, the heat input balance from the upper and lower shoulders deteriorated, internal defects were generated, and the joint strength was inferior.
In Comparative Example 13, since the curvature radii of the convex curves of the upper shoulder and the lower shoulder were both too large, heat input to the thin plate material and the thick plate material was excessive. As a result, the heat-affected zone became large and the joint strength was inferior.
In Comparative Example 14, since the diameters of the upper base and the lower base were too small with respect to the indentation amount, the plate thickness, and the radius of curvature, the base contacted the thick plate and many burrs were generated. As a result, the flow of the member to be joined to the joined portion was insufficient, and the plate thickness at the joined portion was reduced, resulting in poor joint strength.
In Comparative Example 15, since the spiral grooves were not formed on the convex curved surfaces of the upper and lower shoulders, all the members to be joined extruded by both shoulders became burrs. As a result, the joint thickness was inferior because the plate thickness at the joint decreased.

Examples 19-27
An aluminum alloy A5052-O plate material having a thickness of 3.0 mm was used as a thick plate of the members to be joined, and an aluminum alloy A5052-O plate material having a thickness of 1.0 mm was used as a thin plate. These plate materials were bonded by a differential thickness by a bobbin type friction stir welding method. The tensile strength of the A5052-O plate used as the base material is JIS
It was 197 MPa when measured according to Z2241.

In the combination of a thick plate of 3.0 mm and a thin plate of 1.0 mm, the ranges of the curvature radius R _{1 of} the upper shoulder surface and the curvature radius R ₂ of the lower shoulder surface were determined from the above formulas (1) to (4). The step g ₁ of the butt surface on the base side and the step g ₂ of the butt surface on the lower base side are g ₁ = 1.0 mm and g ₂ = 1.0 mm, respectively, and the pushing amount is 1 of the thickness of the thin plate material. If f ₁ = f ₂ = 0.1 mm which is equal to or less than / 10, the range in which the formulas (1) and (3) are satisfied is 0.8 ≦ g _1,2 ≦ 39.1, so R ₁ , R ₂ the range equation (1) and (3), and 20.1 ≦ _{R 1,2} ≦ 82.4.

In the examples, as the curvature radii of the upper and lower shoulder surfaces, a rotary joining tool having three types of shoulder convex curved surfaces of R ₁ = R ₂ = 21, 50, 80 mm within the above range was used. When the upper base diameter D ₁ and the lower base diameter D ₂ at the respective radii of curvature are calculated from the above formulas (5) and (6), D _1,2 ≧ 13.4, 20.9, and 26.4 mm are obtained. Accordingly, D _1,2 = 14, 21, and 27 mm corresponding to the above R _1,2 .

The Archimedean curve was used for the groove provided in the shoulder. The probe radius was r _p = 2.0 mm which is twice the thickness of the thin plate. The shape of the spiral groove composed of two Archimedean curves provided on the shoulder surface is calculated.
In the case of R ₁ = R ₂ = 21 mm, the groove width h is 3 conditions of h = 0.7, 1.0, and 2.0 mm, and the number of rounds of each groove is 2.0, 1.5, and 1.0. To do. When the groove interval under these conditions is calculated from the equation (10), they are all 0.5 mm or more, and there is no problem in processing. Next, when the groove depth d ₀ is calculated from the equation (11), d ₀ > 0.38, 0.34, and 0.24 mm are obtained, and d ₀ = 0.4, 0.4, and 0.3 mm are determined, respectively. .
When R ₁ = R ₂ = 50 mm, the groove width h is 3 conditions of h = 1.0, 1.5, and 2.0 mm, and the number of rounds of each groove is 2.5, 2.0, and 1.5. To do. When the groove interval under these conditions is calculated from the equation (10), they are all 0.5 mm or more, and there is no problem in processing. Next, when the groove depth d ₀ is calculated from the equation (11), d ₀ > 0.37, 0.30, 0.29 mm, and d ₀ = 0.4, 0.4, and 0.3 mm are determined, respectively. .
In the case of R ₁ = R ₂ = 80 mm, the groove width h is 3 conditions of h = 1.0, 1.0, 1.5 mm, and the number of circumferences of each groove is 3.0, 2.5, 2.0. To do. When the groove interval under these conditions is calculated from the equation (10), they are all 0.5 mm or more, and there is no problem in processing. Next, when the groove depth d ₀ was calculated from the equation (11), d ₀ > 0.40, 0.48, and 0.39 mm were obtained, and all were determined to be d ₀ = 0.5 mm. The combinations in each example are summarized in Table 3.

The side surface of the probe was cut by 0.5 mm every 90 ° to make four surfaces flat, and the other surface was cut into screw grooves to form a substantially octagon (eight surfaces). The direction of the screw on each surface was alternately right and left. The length of the probe was 0.8 mm obtained by subtracting the pushing amount of the upper shoulder and the lower shoulder from the thickness of the thin plate.

  The thick plate and the thin plate to be joined were cut into a width of 150 mm and a length of 400 mm, and the long sides were butted and joined so that the shape after joining was a width of 300 mm and a length of 400 mm.

  Using the above nine types of rotary joining tools 34 to 42, the thick plate and the thin plate were subjected to friction stir welding under the conditions of rotational speed: 1000 rpm and joining speed: 300 mm / min. During joining, the rotary joining tool is not tilted on either side of the two plate members and neither before nor after in the joining direction. The rotary welding tool is rotated counterclockwise when viewed from above, and a thin plate is placed on the side where the rotational direction of the rotary welding tool coincides with the welding direction (advance side), and the rotational direction of the rotary welding tool is opposite to the welding direction. A thick plate was placed on the side (retreat side).

In order to measure the joint strength of the joining material thus friction stir welded, a JIS No. 5 type test piece was cut out from each joining material and used as a sample. This sample was cut so that the joining line was positioned at the center of the test piece and the tensile direction in the tensile test was perpendicular to the joining line. About each test piece at room temperature, JIS
A tensile test was performed according to Z2241, and the tensile strength was measured. This tensile strength was defined as joint strength. The ratio of joint strength to base material strength was defined as joint efficiency. Table 6 shows joint strength and joint efficiency.

Comparative Examples 16-24
The same thick plate and thin plate as those used in Examples 19 to 27 were used as the members to be joined, and a friction stir welding test was performed using the following nine types of rotary joining tools different from the examples.

As described above, the range of R ₁ and R ₂ obtained from the above formulas (1) and (3) is 20.1 ≦ R _1,2 ≦ 82.4. As comparative examples, rotary joining tools 43 to 46 in which the curvature radii R _1,2 = 17 mm and 85 mm of the convex curved surface of the upper shoulder outside this range were used (Comparative Examples 16 to 19).

The diameter _D 1 of the upper base and the lower base of each of the radii of curvature, _{D 2} and the equation (5), is calculated from _(6), the diameter _{D 1, 2} of the upper base and the lower base in R 1, 2 = 17 mm is Since D _1,2 ≧ 12.0, D _1,2 = 12 mm, and when R _1,2 = 85 mm, the diameters D _1,2 of the upper base and the lower base are D _1,2 ≧ 27.3. and the _{D 1,2} = 28mm.

Further, R ₁ and R ₂ of Comparative Examples 20 to 23 satisfy R ₁ = R ₂ = 21, 80 mm that satisfy the above R ₁ and R ₂ ranges (20.1 ≦ R _1,2 ≦ 82.4). The diameters D ₁ and ₂ of the upper base and the lower base were D _1,2 = 12 and 24 mm, respectively, and rotary joining tools 50 to 53 that did not satisfy the above formulas (5) and (6) were used. The combinations in each comparative example are summarized in Table 3.

Two grooves provided on the shoulder were provided, and an Archimedean curve was used as in the example. The shape of the spiral groove composed of this Archimedean curve is calculated.
In the case of R _1,2 = 17 mm, the groove width h was set to two conditions of h = 0.5 and 1.0, and the number of groove turns was set to 1.5 and 1.0, respectively. When the groove spacing under these conditions was calculated from the equation (10), it was confirmed that there was no problem with all of 0.5 mm or more. Next, when the groove depth d ₀ is calculated from the equation (11), d ₀ > 0.65 and 0.46 mm, respectively, and d ₀ = 0.7 and 0.5 mm, respectively.
Further, in the case of R _1,2 = 85 mm, the groove width h was set to two conditions of h = 1.0 and 1.5, and the respective groove circumferences were set to 3.0 and 2.0. When the groove spacing under these conditions was calculated from the equation (10), it was confirmed that there was no problem with all of 0.5 mm or more. Next, when the groove depth d ₀ was calculated from the equation (11), d ₀ > 0.42 and 0.40 mm were obtained, respectively, and all were determined to be d ₀ = 0.5 mm.
In the case of R _1,2 = 21 mm and D _1,2 = 12 mm, the groove width h was set to h = 1.0 mm, and the number of circulations of the groove was set to N = 1. When the groove interval under this condition is calculated from the equation (10), it is 0.5 mm or more, and there is no problem. Next, when the groove depth d ₀ is calculated from the equation (11), d ₀ > 0.57 mm, so d ₀ = 1.0 mm.
In the case of R _1,2 = 80 mm and D _1,2 = 24 mm, the groove width h was set to h = 1.0 mm, and the number of circulations of the groove was set to N = 2. When the groove interval under this condition is calculated from the equation (10), it is 0.5 mm or more, and there is no problem. Next, when the groove depth d ₀ is calculated from the equation (11), d ₀ > 0.66 mm, so d ₀ = 1.0 mm.

Furthermore, in Comparative Example 24, the range of R ₁ and R ₂ obtained from the above formulas (1) to (4) (20.1 ≦ R _1,2 ≦ 82.4) was satisfied, and the above formula (5), A rotary joining tool 51 in which R ₁ = R ₂ = 21 mm satisfying (6) and D ₁ = D ₂ = 14 mm and grooves are not provided on both shoulder surfaces was used.

  The friction stir welding tests of Comparative Examples 16 to 24 were performed under the same conditions as in Examples 19 to 27. For the obtained bonding material, the joint strength was measured in the same manner as in Examples 19 to 27 to determine the joint efficiency. The results are shown in Table 6.

  As can be seen from Table 6, in Examples 19 to 27, the joint strength was the same as the base metal strength, and all fractured on the thin plate side, the joint efficiency was 100%, and a high-strength joining material was obtained. Thus, it became clear that the members to be joined that were joined using the rotary joining tool having the shoulder structure defined in the present invention have good joint characteristics.

  On the other hand, in Comparative Examples 16 to 24, the joint efficiency was 93% or less, and fractured at the joint on the thin plate side, and a high-strength joint material was not obtained.

Specifically, in Comparative Example 16, since the curvature radii of the convex curves of the upper shoulder and the lower shoulder were both too small, heat input to the thin plate material and the thick plate material became insufficient. As a result, internal defects occurred and the joint strength was poor.
In Comparative Example 17, the radius of curvature of the convex curve of the upper shoulder is too small, so heat input from the upper shoulder is insufficient, and the radius of curvature of the convex curve of the lower shoulder is too large, so the heat input from the lower shoulder is excessive. It was. As a result, the heat input balance from the upper and lower shoulders was lacking, internal defects were generated, and the joint strength was inferior.
In Comparative Example 18, the heat input from the upper shoulder was excessive because the curvature radius of the convex curved surface of the upper shoulder was too large, and the heat input from the lower shoulder was insufficient because the curvature radius of the convex curved surface of the lower shoulder was too small. . As a result, the heat input balance deteriorated and internal defects were generated, resulting in low joint strength.
In Comparative Example 19, since the curvature radii of the convex curves of the upper shoulder and the lower shoulder were both too large, heat input to the thin plate and the thick plate material was excessive. As a result, the thickness of the joint portion was reduced and the joint strength was reduced.
In Comparative Examples 20 to 23, since the diameters of the upper base and the lower base were too small with respect to the indentation amount, the plate thickness, and the radius of curvature, the base contacted the thick plate and many burrs were generated. As a result, the flow of the member to be joined to the joined portion was insufficient, and the plate thickness at the joined portion was reduced, resulting in poor joint strength.
In Comparative Example 24, since the spiral grooves were not formed on the convex curved surfaces of the upper and lower shoulders, all the members to be joined extruded by both shoulders became burrs. As a result, the joint thickness was inferior because the plate thickness at the joint decreased.

  According to the present invention, in the friction stir welding of the members to be joined having different plate thicknesses, a rotary joining tool is obtained which is easy to control and relatively inexpensive and gives a good joining strength. Thus, a friction stir welding method capable of obtaining a high bonding strength is achieved.

DESCRIPTION OF SYMBOLS 1 ... To-be-joined member 11 ... Thick board to-be-joined member (thick board)
12 ... Thin plate bonded member (thin plate)
DESCRIPTION OF SYMBOLS 11a ... Butt surface of thick board to-be-joined member 12a ... Butt face of thin-plate to-be-joined member 2 ... Backing material 3 ... Rotary joining tool 31 ... Probe 32 ... Upper shoulder 33 ... Upper base 34 ... Lower shoulder 35 ... Lower base 330 ... Large diameter main body 350 ... Hexagonal main body 36, 37, 38, 39 ... (spiral) groove push-in amount of the upper shoulder at 5 ... friction stir welding tool 51.. the upper rotating body 52 ... upper shoulder 53 ... lower rotating body 54 ... bottom shoulder f ₁ ... thin joint member (mm )
f ₂ ... Pushing amount of the lower shoulder in the thin plate joining member (mm)
g ₁ ... Step height of the butting surface at the upper shoulder g ₂ · Step height of the butting surface at the lower shoulder h · Groove width J · Butting portion N · Number of vortex cycles r · · · Distance from origin O in Fig. 4 (variable)
r _L : Radius of projection surface of contact surface of shoulder and plank r _L1 : Radius of projection surface of contact surface of upper shoulder and plank r _L2: Projection of contact surface of lower shoulder and plank Radius of surface r _p ... Probe diameter r _s ... Radius of projection surface of contact surface of shoulder and thin plate r _s1 ... Radius of projection surface of contact surface of upper shoulder and thin plate r _s2 ... Lower shoulder the radius of curvature of the radius R · · · curvature radius of curvature R ₁ · · · upper shoulder of the convex curved surface of the shoulder of the convex curved surface in Figure 4 the radius R ₂ · · · lower shoulder of the convex curved surface of the projection plane of the contact surface of the sheet t: Thickness of the thin plate joining member T: Thickness of the thick plate joining member δ: Spacing of the spiral grooves θ _{1: In} FIG. 3, when the rotary joining tool is pushed in by the pushing amount f ₁ The upper shoulder surface and plank surface contact and upper shoulder At an angle [psi ₁ · · · Figure 3 line and abutting surface connecting the centers of the curved surface forms, in I the rotating welding tool pushing push amount f _1, the upper shoulder surface and the thin surface contact and the upper shoulder Angle θ ₂ formed by the segment connecting the center of the curved surface and the butting surface In FIG. 3, when the rotary joining tool is pushed in by an amount f _{2 of} pushing, the contact between the lower shoulder surface and the thick plate surface and the upper shoulder in the angle [psi ₂ · · · Figure 3 connecting it lines and abutting surface center forms a curved surface, when it rotating welding tool pushing amount f ₂ pushed do, contact of the lower shoulder surface and the thin surface and an upper shoulder Between the line segment connecting the center of the curved surface and the butt surface

Claims (8)

A rotary joining tool used for friction stir welding of butted portions of members to be joined made of metal plates having different plate thicknesses, the upper base portion having a substantially cylindrical shape; provided on the member to be joined side of the upper base portion An upper shoulder; a substantially cylindrical lower base; a lower shoulder provided on the bonded member side of the lower base; and the upper base and the lower connected to each other between a surface of the upper shoulder and a surface of the lower shoulder And a probe hanging concentrically with the base;
The surfaces of the upper shoulder and the lower shoulder each form a convex curved surface toward the abutting portion, and in the convex curved surface, from the outer periphery to the center, and the joined member plasticized by the rotation of the rotary joining tool One or more grooves provided to flow into the interior are formed,
The abutting portion between the joined members is sandwiched between the upper shoulder and the lower shoulder so that the probe is parallel to the abutting surface of the abutting portion, and the upper base portion and the lower base portion do not contact the joined member A rotary joining tool for friction stir welding, wherein the probe moves along the abutting portion while rotating in a state. The curvature radii R ₁ (mm) and R ₂ (mm) of the convex curved surfaces of the upper shoulder and the lower shoulder satisfy the relationships of the following formulas (1) to (4), and the diameter D ₁ of the upper base and the lower base: The rotary joining tool for friction stir welding according to claim 1, wherein (mm) and D ₂ (mm) satisfy the relationships of the following formulas (5) and (6).
[4t ² −f ₁ ² − {(4t ² −f ₁ ² ) ² + 16f ₁ ² (t ² −T ² )} ^1/2 ] / 2 f ₁ ≦ g ₁ ≦ [4t ² −f ₁ ² + {( 4t ² −f ₁ ² ) ² + 16f ₁ ² (t ² −T ² )} ^1/2 ] / 2f ₁
time,
(F ₁ ² + 4t ² ) / 2f ₁ ≦ R ₁ ≦ {(g ₁ + f ₁ ) ² + 20T ² } / 2 (g ₁ + f ₁ )
(1)
If it is outside the above range,
{(G ₁ + f ₁ ) ² + 4T ² } / 2 (g ₁ + f ₁ ) ≦ R ₁ ≦ (f ₁ ² + 20t ² ) / 2f ₁
(2)
And
[4t ² −f ₂ ² − {(4t ² −f ₂ ² ) ² + 16f ₂ ² (t ² −T ² )} ^1/2 ] / 2f ₂ ≦ g ₂ ≦ [4t ² −f ₂ ² + {( 4t ² −f ₂ ² ) ² + 16f ₂ ² (t ² −T ² )} ^1/2 ] / 2f ₂
time,
(F ₂ ² + 4t ² ) / 2f ₂ ≦ R ₂ ≦ {(g ₂ + f ₂ ) ² + 20T ² } / 2 (g ₂ + f ₂ )
(3)
If it is outside the above range,
{(G ₂ + f ₂ ) ² + 4T ² } / 2 (g ₂ + f ₂ ) ≦ R ₂ ≦ (f ₂ ² + 20t ² ) / 2f ₂
(4)
And
D ₁ ≧ 2 {(2R ₁ −g ₁ −f ₁ ) (g ₁ + f ₁ )} ^1/2 (5)
D ₂ ≧ 2 {(2R ₂ −g ₂ −f ₂ ) (g ₂ + f ₂ )} ^1/2 (6)
Where, f ₁ : pressing amount of upper shoulder in thin plate joining member (mm), g ₁ : level difference (mm) of butt surface on upper shoulder side, f ₂ : pressing amount of lower shoulder in thin plate joining member (Mm), g ₂ : level difference (mm) of the abutting surface on the lower shoulder side, t: thickness (mm) of the thin plate joining member, T: thickness (mm) of the thick plate joining member.   The rotary joining tool for friction stir welding according to claim 1 or 2, wherein the upper base has a large-diameter or hexagonal main body on the side opposite to the upper shoulder.   The rotary joining tool for friction stir welding according to any one of claims 1 to 3, wherein the lower base has a large-diameter or hexagonal main body on the side opposite to the lower shoulder. A friction stir welding method for joining a member to be joined by joining a member to be joined made of a metal plate having different plate thicknesses and moving the rotary joining tool along the abutting portion while rotating the rotary joining tool. A substantially cylindrical upper base; an upper shoulder provided on the bonded member side of the upper base; a substantially cylindrical lower base; a lower shoulder provided on the bonded member side of the lower base; A probe connected between a surface of the upper shoulder and a surface of the lower shoulder and hanging concentrically with the upper base and the lower base; and is configured to be integrally rotatable.
The surfaces of the upper shoulder and the lower shoulder each form a convex curved surface toward the abutting portion, and in the convex curved surface, from the outer periphery to the center, and the joined member plasticized by the rotation of the rotary joining tool One or more grooves provided to flow into the interior are formed,
The abutting portion between the joined members is sandwiched between the upper shoulder and the lower shoulder so that the probe is parallel to the abutting surface of the abutting portion, and the upper base portion and the lower base portion do not contact the joined member A friction stir welding method, wherein the probe moves along the abutting portion while rotating in a state. The curvature radii R ₁ (mm) and R ₂ (mm) of the convex curved surfaces of the upper shoulder and the lower shoulder satisfy the relationships of the following formulas (1) to (4), and the diameter D ₁ of the upper base and the lower base: The friction stir welding method according to claim 5, wherein (mm) and D ₂ (mm) satisfy the relationships of the following formulas (5) and (6).
[4t ² −f ₁ ² − {(4t ² −f ₁ ² ) ² + 16f ₁ ² (t ² −T ² )} ^1/2 ] / 2 f ₁ ≦ g ₁ ≦ [4t ² −f ₁ ² + {( 4t ² −f ₁ ² ) ² + 16f ₁ ² (t ² −T ² )} ^1/2 ] / 2f ₁
time,
(F ₁ ² + 4t ² ) / 2f ₁ ≦ R ₁ ≦ {(g ₁ + f ₁ ) ² + 20T ² } / 2 (g ₁ + f ₁ )
(1)
If it is outside the above range,
{(G ₁ + f ₁ ) ² + 4T ² } / 2 (g ₁ + f ₁ ) ≦ R ₁ ≦ (f ₁ ² + 20t ² ) / 2f ₁
(2)
And
[4t ² −f ₂ ² − {(4t ² −f ₂ ² ) ² + 16f ₂ ² (t ² −T ² )} ^1/2 ] / 2f ₂ ≦ g ₂ ≦ [4t ² −f ₂ ² + {( 4t ² −f ₂ ² ) ² + 16f ₂ ² (t ² −T ² )} ^1/2 ] / 2f ₂
time,
(F ₂ ² + 4t ² ) / 2f ₂ ≦ R ₂ ≦ {(g ₂ + f ₂ ) ² + 20T ² } / 2 (g ₂ + f ₂ )
(3)
If it is outside the above range,
{(G ₂ + f ₂ ) ² + 4T ² } / 2 (g ₂ + f ₂ ) ≦ R ₂ ≦ (f ₂ ² + 20t ² ) / 2f ₂
(4)
And
D ₁ ≧ 2 {(2R ₁ −g ₁ −f ₁ ) (g ₁ + f ₁ )} ^1/2 (5)
D ₂ ≧ 2 {(2R ₂ −g ₂ −f ₂ ) (g ₂ + f ₂ )} ^1/2 (6)
Where, f ₁ : pressing amount of upper shoulder in thin plate joining member (mm), g ₁ : level difference (mm) of butt surface on upper shoulder side, f ₂ : pressing amount of lower shoulder in thin plate joining member (Mm), g ₂ : level difference (mm) of the abutting surface on the lower shoulder side, t: thickness (mm) of the thin plate joining member, T: thickness (mm) of the thick plate joining member.   The friction stir welding method according to claim 5 or 6, wherein the upper base has a large-diameter or hexagonal main body on the side opposite to the upper shoulder.   The friction stir welding method according to any one of claims 5 to 7, wherein the lower base includes a main body having a large diameter or a hexagonal shape on the side opposite to the lower shoulder.

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